We propose to determine the chiral conformation of 11-cis retinal analogues that bind to opsin to form artificial visual pigments. We will synthesize visual pigment analogues whose absorption spectra (or the spectra of its low temperature intermediates) or circular dichroism spectra are dependent on the twisted conformation of the chromophore about the 6-7 and/or 12-13 single bonds. Retinals enriched with C13 at C-15, C-14, 5-Me and other carbons will be synthesized and the C13 nuclear magnetic resonance measured. Studies on chemical shifts and T1- relaxation time of rhodopsin are expected to give information, otherwise difficult to obtain, on the conformations of the various bound and unbound retinals and their environments. The results of these studies will give us the entire chiral conformation of the visual pigment chromophores which will in turn help explain the absorption and circular dichroism spectra of both rhodopsin and its low temperature intermediates, and contribute to the description of the binding site for retinal in opsin.